The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
In general, DVB-H systems can be found in three different types of integrated mobile TV tuners: (a) Direct conversion for DVB-H, (b) Direct conversion for multi-standard reception, and (c) Mixed direct conversion and low-IF (low intermediate frequency) for multi-standard reception. It is advantageous for a multi-standard reception mobile TV tuner to adopt direct conversion structure for DVB-H reception and low-IF structure for the Sistema Brasileiro de Televisão Digital (ISDB-T) and terrestrial digital multimedia broadcasting (T-DMB) standards, as DVB-H is wide band and ISDB-T & T-DMB are narrow band systems.
However, it is not power-efficient to reconfigure a complex band-pass filter used in the low-IF mode to act as a low-pass filter for DVB-H direct conversion mode. This is because the active complex band-pass filters used in the low-IF mode require at least two active components (i.e., amplifiers) per biquadratic filter (hereinafter, “biquad”) for each path of the filter, whereas the low-pass filter for DVB-H may be realized by biquad low-pass filters utilizing a single active component per biquad. A biquad is a second order filter having two poles and two zeros.
Also, the significantly distinct bandwidths of the various standards hinder improving the same filter for the two modes. Two different filters may be used: one for the low-IF mode and one for the DVB-H direct conversion mode, wherein the unused filter goes into a power saving mode. While a dual-filter system would be achieved at the cost of area, a significant part of the area is often occupied by capacitors, which may be shared between the two filters, thereby significantly reducing the overall area of the system.
For filters that are part of a DVB-H receiver or a multi-standard mobile TV integrated direct-conversion receiver, demanding constraints are placed on the filter's linearity and power consumption.
The present disclosure is directed to a low power low-pass filter based on a transresistance amplifier (TRA) providing significant power saving compared with the available solutions. An FDTRA is a fully differential current-to-voltage converter, whose gain is set based on the conversion resistance. FDTRAs are associated with voltage buffered outputs that can drive large capacitive loads without slewing.